Servo driven compliant mechanism

ABSTRACT

A servo driven compliant mechanism is provided. The servo driven compliant mechanism includes a holder, a first pivot, a grinding tool, a posture sensor, a displacement sensor, an inner frame, and a first servomotor. The first pivot is perpendicular to an axial direction of the grinding tool. The posture sensor is used for sensing a posture of the grinding tool and sending a posture signal to be transformed into a torque compensation value for an effect of gravity. The displacement sensor is used for sensing a displacement of the grinding tool along the first pivot. The grinding tool is disposed in the inner frame, and the first pivot is movably disposed in the inner frame. The first servomotor is disposed in the inner frame and drives the grinding tool to rotate along the first pivot according to the torque compensation value and the displacement.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 109140253, filed on Nov. 18, 2020. The entire content of the above identified application is incorporated herein by reference.

Some references, which may include patents, patent applications and various publications, may be cited and discussed in the description of this disclosure. The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to the disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a servo driven compliant mechanism belonging to a field of mechanical processing, and more particularly to a grinding or polishing device with automatic compensation function for removing burrs from workpieces.

BACKGROUND OF THE DISCLOSURE

Post-processing in manufacturing refers to processes such as deburring, surface grinding, polishing, etc., that are performed on a workpiece after an initial fabrication thereof. However, an automatic process is difficult to be performed due to different shapes of various workpieces, and a manual operation of pneumatic tools or electric tools for processing is heavily relied upon. Such manual processing methods have poor efficiency and result in unstable quality.

With the development of industrial automation, automatic deburring has been developed to achieve better production efficiency, but a key issue in the automatic deburring is how to automatically adjust a pressing force between a grinding tool and the workpiece.

Therefore, how to improve and enhance effectiveness of a compliant mechanism of a grinding tool has become one of issues to be addressed in the related field.

SUMMARY OF THE DISCLOSURE

In response to the above-referenced technical inadequacies, the present disclosure provides a servo driven compliant mechanism, which can output stable pressing force in response to uneven surfaces or dimensional changes, and compensate for an effect of gravity on output force in various postures of a grinding tool, such that a particular demand on a grinding quality can be achieved.

In one aspect, the present disclosure provides a servo driven compliant mechanism, which includes a holder, a first pivot, a grinding tool, a posture sensor, a displacement sensor, an inner frame, and a first servomotor. The first pivot is fixedly connected to the holder. The grinding tool is fixed in the holder. The first pivot is perpendicular to an axial direction of the grinding tool. The posture sensor is used for sensing a posture of the grinding tool and sending a posture signal to be transformed into a torque compensation value for an effect of gravity. The displacement sensor is used for sensing a displacement of the grinding tool along the first pivot. The grinding tool is disposed in the inner frame, and the first pivot is movably disposed in the inner frame. The first servomotor is disposed in the inner frame and drives the grinding tool to rotate along the first pivot according to the torque compensation value and the displacement, so that a pressing force output by the grinding tool is not affected by gravity in any posture of the grinding tool.

In certain embodiments, the servo driven compliant mechanism further includes an outer frame and a second servomotor. The inner frame is disposed in the outer frame, the inner frame includes a second pivot, and the second pivot is perpendicular to the first pivot. The second pivot of the inner frame is rotatably disposed in the outer frame. The second servomotor is disposed in the outer frame, and the second servomotor drives the grinding tool to rotate along the second pivot according to the torque compensation value and the displacement, so that the pressing force output by the grinding tool is not affected by gravity in any posture of the grinding tool.

Therefore, one of the beneficial effects of the present disclosure is that, the servo driven compliant mechanism provided by the present disclosure includes at least one motor, the posture sensor, and the displacement sensor. The effect of gravity on the grinding tool at different angles can be compensated through a cooperation of the posture sensor and the motor. Moreover, an offset of a zero point of the grinding tool can be achieved by a cooperation of the displacement and the motor. In this way, in the servo driven compliant mechanism provided by the present disclosure, the pressing force between the grinding tool and a workpiece can be maintained when the servo driven compliant mechanism is in various postures or at different angles.

These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments may be better understood by reference to the following description and the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a servo driven compliant mechanism according to a first embodiment of the present disclosure;

FIG. 2 is a schematic view showing a compensation for gravity of a grinding tool according to the first embodiment of the present disclosure;

FIG. 3 is a schematic view showing a displacement sensing of the grinding tool according to the first embodiment of the present disclosure;

FIG. 4 is a schematic view of the grinding tool having an indicator disposed thereon according to the first embodiment of the present disclosure;

FIG. 5 is a schematic view of the grinding tool cooperating with a display device according to the first embodiment of the present disclosure;

FIG. 6 is a schematic cross-sectional view of a servo driven compliant mechanism according to a second embodiment of the present disclosure; and

FIG. 7 is a schematic view showing a servo control of the servo driven compliant mechanism according to the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a”, “an”, and “the” includes plural reference, and the meaning of “in” includes “in” and “on”. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.

The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first”, “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.

First Embodiment

Referring to FIG. 1 to FIG. 3, the present disclosure provides a servo driven compliant mechanism 1 a, which includes a holder 10, a grinding tool 12, a posture sensor 18, a displacement sensor 19, an inner frame 20, an outer frame 30, a first servomotor 40, and a second servomotor 50.

The grinding tool 12 is clamped in the holder 10. A first pivot 11 is fixedly connected to the holder 10, and the first pivot 11 is perpendicular to an axial direction of the grinding tool 12. The grinding tool 12 can be a pneumatic grinding tool or an electric grinding tool, and a rotational speed of the electric grinding tool is adjustable.

In the present embodiment, the holder 10 and the grinding tool 12 are disposed in the inner frame 20, and the first pivot 11 of the grinding tool 12 is moveably disposed in the inner frame 20. In other words, the grinding tool 12 rotates in the inner frame 20 along the first pivot 11 so as to adjust an angle of the grinding tool 12. The inner frame 20 can include one pair of first bearings 22 for supporting the first pivot 11.

The posture sensor 18 is used for sensing a posture of the grinding tool 12 and sending a posture signal to be transformed into a torque compensation value for an effect of gravity. For example, the posture signal can be output to an external processor and calculated by the external processor to obtain the torque compensation value. Then the torque compensation value can be transmitted to the first servomotor 40. The posture sensor 18 can be disposed at any position of the grinding tool 12 or the servo driven compliant mechanism 1 a. The displacement sensor 19 is used for sensing a displacement of the grinding tool 12 along the first pivot 11.

The first servomotor 40 is disposed in the inner frame 20. The first servomotor 40 drives the grinding tool 12 to rotate along the first pivot 11 according to the torque compensation value and the displacement, so that a pressing force output by the grinding tool 12 is not affected by gravity in any posture of the grinding tool 12.

In the present embodiment, the first servomotor 40 drives the grinding tool 12 in an indirect manner. More specifically, the first servomotor 40 and the first pivot have a first gear assembly G1 arranged therebetween. The first gear assembly G1 transmits force generated by the first servomotor 40 to the first pivot 11. More specifically, the first gear assembly G1 includes a first driven gear 112 that is connected to the first pivot 11, and a first driving gear 42 that is connected to the first servomotor 40. More specifically, the first driving gear 42 is connected to a first rotary shaft 41 of the first servomotor 40, and the first driven gear 112 is meshingly engaged to the first driving gear 42. The first pivot 11 extends to an outer side of the inner frame 20, and the first servomotor 40 is disposed on the outer side of the inner frame 20 and the first servomotor 40 is adjacent to the first pivot 11. The first servomotor 40 can be a rotary servomotor having a rotary shaft that is parallel to the first pivot 11.

The inner frame 20 is disposed in the outer frame 30. The inner frame 20 includes a second pivot 21, and the second pivot 21 is perpendicular to the first pivot 11. The second pivot 21 of the inner frame 20 is rotatably disposed in the outer frame 30. In other words, the inner frame 20 rotates in the outer frame 30 along the second pivot 21 so as to deflect the inner frame 20 to various angles, and also to deflect the grinding tool 12 along the second pivot 21. The outer frame 30 can include one pair of second bearings 32 for supporting the second pivot 21.

The second servomotor 50 is disposed in the outer frame 30. In the present embodiment, the second servomotor 50 drives the inner frame 20 in such a manner that the second servomotor 50 and the second pivot 21 have a second gear assembly G2 arranged therebetween, and the second gear assembly G2 transmits force generated by the second servomotor 50 to the second pivot 21. More specifically, the second gear assembly G2 includes a second driven gear 212 that is connected to the second pivot 21, and a second driving gear 52 that is connected to the second servomotor 50. More specifically, the second driving gear 52 is connected to a second rotary shaft 51 of the second servomotor 50, and the second driven gear 212 is meshingly engaged to the second driving gear 52. The second pivot 21 extends to an outer side of the outer frame 30, and the second servomotor 50 is disposed on the outer side of the outer frame 30 and is adjacent to the second pivot 21. The second servomotor 50 can be a rotary servomotor having a rotary shaft that is parallel to the second pivot 21.

The servo driven compliant mechanism of the present disclosure drives the grinding tool 12 to rotate along the second pivot 21 according to the torque compensation value and the displacement, so that the pressing force output by the grinding tool 12 is not affected by gravity in any posture of the grinding tool 12.

As shown in FIG. 2, the servo driven compliant mechanism can include a housing H for accommodating the components described above, and the posture sensor 18 can be disposed in the housing H for sensing the posture of the grinding tool 12. In the present embodiment, the posture of the grinding tool 12 can be sensed and the effect of the gravity can be compensated through the posture sensor 18. The posture sensor 18 can be, for example, a nine-axis module that includes a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer, for sensing a yaw motion, a roll motion, and a pitch motion of the grinding tool 12. However, the present disclosure is not limited thereto. In addition, the posture sensor 18 can also include a BLUETOOTH® module to wirelessly send the posture signal.

As shown in FIG. 2, a compensation for the gravity of the present embodiment is exemplarily described as follows. Given that an inclined angle of the grinding tool 12 detected by the posture sensor 18 is θ, the pressing force of the grinding tool 12 is FN, a distance from a point of application of the grinding tool 12 to a center of rotation C1 along an axial direction is L1, a floating mass of the grinding tool 12 is Mg, and a distance from a floating center of mass C2 to the center of rotation C1 is L2, a formula for a torque command Tc of the present embodiment can be expressed as follows.

Tc=FN*L1+Mg*cos θ*L2.

As shown in FIG. 3, in the present embodiment, the grinding tool 12 includes the displacement sensor 19 for sensing the displacement of the grinding tool 12 along the pivot. The displacement sensor 19 can be a rotary encoder disposed on a same axis as the pivot, or can be designed in various forms, such as a laser displacement sensor, an ultrasonic displacement sensor, an optical displacement sensor, and the three-axis accelerometer, but is not limited thereto. In addition, the displacement sensor 19 can also include the BLUETOOTH® module to wirelessly send a displacement signal that corresponds to the displacement of the grinding tool 12 along the pivot. The displacement signal can be, for example, output to the external processor and calculated by the external processor to obtain a compensation for the torque command Tc. Then the compensation for the torque command Tc can be transmitted to the first servomotor 40. Accordingly, the compensation for the torque command Tc can be provided by the displacement sensor 19, and a greater amount of the compensation is provided when a displacement angle increases.

As shown in FIG. 4, the servo driven compliant mechanism can further include an indicator 101. The indicator 101 outputs an indication signal according to a comparison value obtained by comparing the displacement signal and a predetermined displacement. For example, when the displacement of the grinding tool 12 is detected to be greater than the predetermined displacement, the indication signal is sent to the indicator 101, such as using an indicator light to emit red light. When the grinding tool 12 is detected to be less than the predetermined displacement, the indication signal is sent to indicator 101, such as using an indicator light to emit green light. In this way, the present disclosure can be applied to set an amount of interference between the grinding tool 12 and a workpiece when manually setting a grinding path.

However, the present disclosure is not limited to the above. As shown in FIG. 5, the servo driven compliant mechanism further includes a display device 60 for receiving the indication signal and for displaying a current status of the grinding tool 12 according to the indication signal.

Furthermore, the servo driven compliant mechanism 1 a of the present embodiment described above has two rotary shafts, but the present disclosure is not limited thereto. According to practical requirements, the servo driven compliant mechanism of the present disclosure can also have a single rotary shaft. For example, the servo driven compliant mechanism only includes the grinding tool 12, the posture sensor 18, the displacement sensor 19, the inner frame 20, and the first servomotor 40. That is, the outer frame and the second servomotor are omitted in the servo driven compliant mechanism.

Second Embodiment

Referring to FIG. 6, FIG. 6 is a schematic cross-sectional view of a servo driven compliant mechanism 1 b according to a second embodiment of the present disclosure. The difference between the present embodiment and the first embodiment is that, the servo driven compliant mechanism of the present embodiment is a servo driven compliant mechanism of a direct-drive type; that is, the gear assemblies described above can be omitted in the present embodiment. In other words, a motor of the present embodiment drives the grinding tool 12 in a manner different from that described in the previous embodiment. More specifically, the first servomotor 40 includes a first driving member 43, and the first driving member 43 is connected to the grinding tool 12. The first servomotor 40 of the present embodiment can be a linear motor or a rotary motor cooperating with a linear transmission mechanism. For example, the driving member of the linear motor can be a ball screw shaft, and the ball screw shaft is directly connected to the grinding tool 12. The ball screw shaft can generate a linear motion so as to drive the grinding tool 12 to rotate along the first pivot 11 and relative to the inner frame 20. Alternatively, the first driving member 43 can be the linear transmission mechanism. A rotation of the rotary motor is converted to a linear displacement through the linear transmission mechanism, and can also drive the grinding tool 12 to rotate relative to the inner frame 20.

Likewise, the second gear assembly can be omitted in the present disclosure. The second servomotor 50 includes a second driving member 53, and the second driving member 53 is connected to the inner frame 20. The second servomotor 50 can be the linear motor or the rotary motor cooperating with the linear transmission mechanism. The second driving member 53 can be the ball screw shaft or the linear transmission mechanism.

Referring to FIG. 7, FIG. 7 is a schematic view showing a servo control of the servo driven compliant mechanism according to the present disclosure. The displacement sensor 19 can be an encoder E, and the encoder E can be built into or added to a servomotor M. A servo computer R receives a displacement of the servomotor M, and then transmits an integrated torque compensation value and the displacement to the servomotor M.

[Beneficial Effects of the Embodiments]

In conclusion, one of the beneficial effects of the present disclosure is that, the servo driven compliant mechanism provided by the present disclosure includes at least one motor, the posture sensor, and the displacement sensor. The effect of gravity on the grinding tool at different angles can be compensated by a cooperation of the posture sensor and the motor. Moreover, an offset of a zero point of the grinding tool can be achieved by a cooperation of the displacement and the motor. In this way, the servo driven compliant mechanism provided by the present disclosure can adjust an output speed or force of the grinding tool in various postures or at different angles.

The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope. 

What is claimed is:
 1. A servo driven compliant mechanism, comprising: a holder; a first pivot fixedly connected to the holder; a grinding tool fixed in the holder, wherein the first pivot is perpendicular to an axial direction of the grinding tool; a posture sensor used for sensing a posture of the grinding tool and sending a posture signal to be transformed into a torque compensation value for an effect of gravity; a displacement sensor for sensing a displacement of the grinding tool along the first pivot; an inner frame, wherein the grinding tool is disposed in the inner frame, and the first pivot is movably disposed in the inner frame; and a first servomotor disposed in the inner frame, wherein the first servomotor drives the grinding tool to rotate along the first pivot according to the torque compensation value and the displacement, so that a pressing force output by the grinding tool is not affected by gravity in any posture of the grinding tool.
 2. The servo driven compliant mechanism according to claim 1, wherein the grinding tool further includes an indicator, and the indicator outputs an indication signal according to a comparison value obtained by comparing a displacement signal that corresponds to the displacement of the grinding tool along the first pivot and a predetermined displacement.
 3. The servo driven compliant mechanism according to claim 2, further comprising: a display device for receiving the indication signal and for displaying a current status of the grinding tool according to the indication signal.
 4. The servo driven compliant mechanism according to claim 1, wherein the first servomotor and the first pivot have a first gear assembly arranged therebetween, and the first gear assembly transmits force generated by the first servomotor to the first pivot.
 5. The servo driven compliant mechanism according to claim 4, wherein the first gear assembly includes a first driven gear that is connected to the first pivot, and a first driving gear that is connected to the first servomotor; wherein the first driven gear is meshingly engaged to the first driving gear.
 6. The servo driven compliant mechanism according to claim 1, wherein the first servomotor includes a first driving member, and the first driving member is connected to the grinding tool.
 7. The servo driven compliant mechanism according to claim 1, further comprising: an outer frame; and a second servomotor; wherein the inner frame is disposed in the outer frame, the inner frame includes a second pivot, and the second pivot is perpendicular to the first pivot; wherein the second pivot of the inner frame is rotatably disposed in the outer frame; wherein the second servomotor is disposed in the outer frame, and the second servomotor drives the grinding tool to rotate along the second pivot according to the torque compensation value and the displacement, so that the pressing force output by the grinding tool is not affected by gravity in any posture of the grinding tool.
 8. The servo driven compliant mechanism according to claim 7, wherein the second servomotor and the second pivot have a second gear assembly arranged therebetween, and the second gear assembly transmits force generated by the second servomotor to the second pivot.
 9. The servo driven compliant mechanism according to claim 8, wherein the second gear assembly includes a second driven gear that is connected to the second pivot, and a second driving gear that is connected to the second servomotor; wherein the second driven gear is meshingly engaged to the second driving gear.
 10. The servo driven compliant mechanism according to claim 7, wherein the second servomotor includes a second driving member, and the second driving member is connected to the inner frame. 